When gluten-free flours are free from contamination with gluten, are suitable for people with gluten-related disorders, such as coeliac disease, non-celiac gluten sensitivity or wheat allergy sufferers, among others.[14][15][16][17] Contamination with gluten-containing cereals can occur during grain harvesting, transporting, milling, storing, processing, handling and/or cooking.[17][18][19] Acorn flour is made from ground acorns and can be used as a substitute for wheat flour. It was used by Native Americans. Koreans also use acorn flour to make dotorimuk. Almond flour is made from ground almonds. Amaranth flour is a flour produced from ground amaranth grain. It was commonly used in pre-Columbian meso-American cuisine and was originally cultivated by the Aztecs. It is becoming more and more available in speciality food shops. Banana flour has been traditionally made of green bananas for thousands of years and is currently popular both as a gluten-free replacement for wheat flour and as a source of resistant starch. Bean flour is a flour produced from pulverized dried or ripe beans. Garbanzo and fava bean flour is a flour mixture with a high nutritional value and strong aftertaste. Brown rice flour is of great importance in Southeast Asian cuisine. Edible rice paper can be made from it. Buckwheat flour is used as an ingredient in many pancakes in the United States. In Japan, it is used to make a popular noodle called soba. In Russia, buckwheat flour is added to the batter for pancakes called blinis which are frequently eaten with caviar. Buckwheat flour is also used to make crêpes bretonnes in Brittany. On Hindu fasting days (Navaratri mainly, also Maha Shivaratri), people eat food made with buckwheat flour. The preparation varies across India. The most famous dishes are kuttu ki puri and kuttu pakoras. In most northern and western states the usual term is kuttu ka atta. Cassava flour is made from the root of the cassava plant. In a purified form (pure starch), it is called tapioca flour (see in list below). Chestnut flour is popular in Corsica, the Périgord, and Lunigiana for breads, cakes and pastas. It is the original ingredient for polenta, still used as such in Corsica and other Mediterranean locations. Chestnut bread keeps fresh for as long as two weeks.[20] In other parts of Italy it is mainly used for desserts. Chickpea flour (also known as gram flour or besan) is of great importance in Indian cuisine, and in Italy, where it is used for the Ligurian farinata. Chuño flour is made from dried potatoes in various countries of South America.